Environment is shared across all document windows #51
Description
When having multiple documents open in separate windows under Red Window, the environment is incorrectly shared between them. For example, triggering a search in one file causes all open windows to also go to the search page.
This is mostly caused by the way the environment is instantiated, and that it's not tied to their respective scenes. Ideally, we can use @FocusedValue and the .focusSceneValue APIs to use the focus system instead of a shared instance declared in the app.